THERMODYNAMIC AND KINETIC ANALYSES OF SYNTHESIZING ZrB2@Al(OH)3–Y(OH)3 CORE–SHELL COMPOSITE PARTICLES

ZrB2 has some excellent performances, but it is easily oxidized at high temperatures to impact the high-temperature strength, which restricts its applied range. To protect from the oxidization and improve the strength of ZrB2 at high temperature, the surface of ZrB2 particles is coated with the Al(OH)3–Y(OH)3 shell to synthesize ZrB2@Al(OH)3–Y(OH)3 core–shell composite particles. Through the thermodynamic and kinetic analyses of the heterogeneous nucleation and homogeneous nucleation, the concentration product of precursor ion (Y3+ or Al3+) and OH- (Qi) must be greater than the solubility product (Ksp), respectively; the conditions of Y3+ and Al3+ are reached to produce Al(OH)3–Y(OH)3 shell on the ZrB2 surface between the Y3+ line and the AlO2- line. Through TEM and XRD analyses, ZrB2@Al(OH)3–Y(OH)3 core–shell composite particles are successfully synthesized by the co-precipitation method, the shell layer quality is better at pH = 9, which established the foundation for preparing high-performance YAG/ZrB2 and Al2O3–YAG/ZrB2 multiphase ceramic materials.